Failure of High-Temperature Microwave-Infrared Stealth Coatings Under Thermal Cycling and Constant-Temperature Loads

Multilayer stealth coatings in aircraft engines are susceptible to spallation under extreme thermal conditions. In order to optimize the coating's fabrication and to lay the foundation for lifetime prediction models, this study investigated the failure mechanisms of a high-temperature microwave-infrared stealth coating (HTMISC) through 1150°C cyclic thermal and constant-temperature tests. Focusing on two poorly bonded interfaces, the top and bottom interfaces of the inner thermal barrier layer (INN, yttria-stabilized zirconia), systematic analyses examined HTMISC microstructure evolution, macroscopic failure morphology, dielectric layer (DIE, alumina) sintering, and bonding layer (BON, NiCrAlY) oxidation. The results showed that, when quantified by equivalent thermal exposure time, the timing of delamination at the DIE–INN interface differed significantly between cyclic thermal and constant-temperature conditions. Thermal mismatch stress imposed by thermal cycling was identified as the critical factor causing premature failure of HTMISC at this interface. Additionally, under constant-temperature loading, rapid mixed oxide (MO) growth intensified INN stress, while the high coverage of friable MO reduced the interfacial adhesive strength. These factors collectively promoted HTMISC spallation at the INN–TGO interface.